Effect of Temperature on Micromechanical Properties of Pol-yvinyl Alcohol Fiber–Matrix interface and Uniaxial Tensile Properties of High-Ductility Cementitious Composites

This study investigated the effects of temperature on the tensile strength of polyvinyl alcohol (PVA) fibers, micromechanical properties of the fiber–matrix interface, and macroscopic uniaxial tensile properties of high-ductility cementitious composites (HDCC). In particular, the following values of the temperature of different regions and the glass transition temperature of PVA fibers were selected: –30 °C, 0 °C, 20 °C, 60 °C, and 180 °C. Thermogravi-metric analysis and differential scanning calorimetry of PVA fibers were carried out using a synchronous thermal analyzer. In addition, the micromorphology of failure fibers and the fiber–matrix interface was observed using a scanning electron microscope. The results showed that when taking the tensile strength at 20 °C as a reference value, after heat treatment at –30 °C, 0 °C, 60 °C, and 180 °C, the average tensile strength of PVA fibers was 86%, 89%, 88%, and 60% of that at 20 °C, respectively. The ultimate tensile strain value of HDCC was closely related to the treatment temperature: it was the largest at 0 °C; its values at –30 °C and 60 °C were essentially equivalent, its value at 20 °C was small, and its value was the smallest at 180 °C. It can be concluded that after the heat treatment, the tensile strength of PVA fibers decreases to some extent, and there is a piecewise linear relationship between the fiber tensile strength and temperature. Hence, an appropriate heat treatment can reduce the chemical debonding energy and increase the frictional bond strength at the onset of fiber slippage. At the same time, the effect of temperature on the ultimate tensile strain of HDCC is opposite to that on the chemical debonding energy of the fiber–matrix interface.